Super Subtraction Strategies: Taking Away from Teen Numbers!

Math Grades 1st Grade 4:03 Video
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Lesson Description

Learn how to subtract from teen numbers like 14 by breaking down the subtraction into smaller steps. We'll use groups of ten and ones to help us!

Video Resource

Subtracting 14 - 6 | Addition and subtraction within 20 | Early Math | Khan Academy

Khan Academy

Duration: 4:03
Watch on YouTube

Key Concepts

  • Decomposing numbers (breaking them apart)
  • Subtracting from ten
  • Understanding place value (tens and ones)

Learning Objectives

  • Students will be able to decompose a number (like 6) to subtract it from a teen number (like 14).
  • Students will be able to subtract from ten.
  • Students will be able to use objects to represent subtraction.

Educator Instructions

  • Introduction (5 mins)
    Start by reviewing what it means to subtract. Ask students: 'What happens when we subtract?' (We take away!). Then, show them the Khan Academy video 'Subtracting 14 - 6' (link provided) and tell them to watch carefully how the person in the video takes away from the group of objects.
  • Understanding Tens and Ones (10 mins)
    Review the concept of tens and ones. Ask students: 'How many tens are in the number 14?' (1 ten) 'How many ones are in the number 14?' (4 ones). Use manipulatives like blocks or counters to show 14 as one group of ten and four single ones.
  • Subtracting by Decomposing (15 mins)
    Explain that subtracting 6 from 14 can be tricky, but we can make it easier by breaking down the 6. Like in the video, demonstrate subtracting 2 from 14 first to get to 12. Then, subtract 4 more (because 2 + 4 = 6). Use manipulatives again to show this process. Say: 'First we take away 2, now we have 12. Then we take away 4, and we have 8!' Repeat with other numbers, like subtracting 5 from 13 (subtract 3 to get to 10, then subtract 2 more).
  • Practice Time (15 mins)
    Give students worksheets with subtraction problems similar to the ones in the video (e.g., 12 - 4, 11 - 3, 15 - 7). Encourage them to use manipulatives or draw pictures to help them solve the problems. Walk around the classroom to assist students and answer questions.
  • Wrap Up (5 mins)
    Review the key concepts of the lesson. Ask students to explain in their own words how they can break down numbers to make subtraction easier. Collect worksheets for assessment.

Interactive Exercises

  • Number Line Subtraction
    Use a number line from 0 to 20. Have students practice subtracting by hopping back on the number line. For example, to subtract 5 from 12, they would start at 12 and hop back 5 spaces.
  • Subtraction Stories
    Create simple subtraction word problems (e.g., 'I have 13 cookies and I eat 4. How many cookies do I have left?') and have students solve them using drawings or manipulatives.

Discussion Questions

  • Why is it helpful to break down a subtraction problem into smaller steps?
  • Can you think of another way to subtract 6 from 14? Is there a different number you could take away first?
  • How does knowing about tens and ones help us with subtraction?

Skills Developed

  • Subtraction within 20
  • Problem-solving
  • Number sense
  • Decomposition of numbers
  • Critical Thinking

Multiple Choice Questions

Question 1:

What is 14 made of?

Correct Answer: 1 ten and 4 ones

Question 2:

If you have 12 cookies and you eat 3, how many cookies do you have left?

Correct Answer: 9

Question 3:

What is 10 - 2?

Correct Answer: 8

Question 4:

Which is the same as 11 - 4?

Correct Answer: 11 take away 4

Question 5:

If you take away 5 from 15, what do you have?

Correct Answer: 10

Question 6:

What is 13 - 3?

Correct Answer: 10

Question 7:

Which number is bigger, 10 or 6?

Correct Answer: 10

Question 8:

If you have 11 apples and give 2 away, how many do you have?

Correct Answer: 9

Question 9:

What is 12 - 2?

Correct Answer: 10

Question 10:

Which is the same as 14 take away 4?

Correct Answer: 14 - 4

Fill in the Blank Questions

Question 1:

14 has 1 _____ and 4 ones.

Correct Answer: ten

Question 2:

12 - 2 = _____.

Correct Answer: 10

Question 3:

Taking away means we _____ from a number.

Correct Answer: subtract

Question 4:

13 - 4 = 9. We say 13 take away 4 is _____.

Correct Answer: 9

Question 5:

15 - 5 = _____.

Correct Answer: 10

Question 6:

If you have 11 toys and lose 3, you have _____ toys left.

Correct Answer: 8

Question 7:

10 - 1 = _____.

Correct Answer: 9

Question 8:

14 - 6 = _____

Correct Answer: 8

Question 9:

When we subtract, the number gets _____.

Correct Answer: smaller

Question 10:

We can break apart numbers to make it easier to _____.

Correct Answer: subtract

Educational Standards

CCSS.Math.Content.1.OA.C.6:Add and subtract within 20, demonstrating fluency for addition and subtraction within 10. Use strategies such as counting on; making ten (e.g., 8 + 6 = 8 + 2 + 4 = 10 + 4 = 14); decomposing a number leading to a ten (e.g., 13 - 4 = 13 - 3 - 1 = 10 - 1 = 9); using the relationship between addition and subtraction (e.g., knowing that 8 + 4 = 12, one knows 12 - 8 = 4); and creating equivalent but easier or known sums (e.g., adding 6 + 7 by creating the known equivalent 6 + 6 + 1 = 12 + 1 = 13). CCSS.Math.Content.1.NBT.B.2.B:The numbers from 11 to 19 are composed of a ten and one, two, three, four, five, six, seven, eight, or nine ones. CCSS.Math.Content.1.OA.A.1:Use addition and subtraction within 20 to solve word problems involving situations of adding to, taking from, putting together, taking apart, and comparing, with unknowns in all positions, e.g., by using objects, drawings, and equations with a symbol for the unknown number to represent the problem.

Teaching Materials

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